A reactor is one of the parts used in a voltage conversion circuit that boosts/lowers a voltage. For example, JP 2012-65453A discloses a reactor for a multiple-phase converter including a core and coils of a plurality of phases that are wound around the core and are magnetically coupled to each other. A reactor (10) for a two-phase converter (two-phase magnetic coupling reactor) described in JP 2012-65453A includes a core (12) and coils (14, 16) of two phases that are wound around the core (12). The core (12) includes a pair of T-shaped portions (20, 22) that each have a T shape and that have a base portion (26) and a central leg portion (28) that projects from the central portion of the base portion (26), and two linear I-shaped portions (24). The T-shaped portions (20, 22) are disposed such that the front ends of the central leg portions (28) are opposed to each other with a gap space (32) therebetween. The I-shaped portions (24) are each coupled to the end portions (end leg elements (30)) of the T-shaped portions (20, 22) via gap plates (18), and are disposed so as to be parallel to each other. In the core (12), two end leg portions (34) is constituted by the I-shaped portions (24) that are located on both sides of the central leg portion (28), and coils (14, 16) are respectively disposed around the end leg portions (34). With this configuration, the size of a reactor can be reduced compared with a single-phase reactor by disposing a plurality of coils in the same core and magnetically coupling the coils to each other.
Smaller sizes are in demand for converters (power conversion devices). In particular, the sizes of vehicle-mounted converters (power conversion devices) can be, in some embodiments, further reduced because an installation space is strictly limited.
A reactor in which a plurality of coils is disposed in the same core and magnetically coupled to each other uses an inductance as well as a coupling coefficient between the coils as important parameters. As described above, the reactor described in JP 2012-65453A is configured such that the core has three magnetic leg portions, namely, the central leg portion of the T-shaped portion and two end leg portions (I-shaped portions) located on both sides thereof, and the coils are respectively disposed in the end leg portions.
In the core, a coupling magnetic path that magnetically couples the coils to each other is formed using the base portions of the T-shaped portions and the end leg portions, and a leakage magnetic path in which a magnetic flux that is produced by the coils leaks is formed using the central leg portion. In this reactor, an inductance and a coupling coefficient can be adjusted by a gap space provided in the central leg portion. However, in this reactor, the core has the central leg portion for adjusting a coupling coefficient in addition to the end leg portions around which the coils are disposed, thus making it difficult to further reduce the size of the reactor.